1. Field of the Invention
The present invention relates to an input device which performs input operation of operation information by using an electrostatic sensor. More particularly, the present invention relates to an input device suitable for improving visibility of an input operation unit by means of an instruction display and an illumination unit.
2. Description of the Related Art
Generally, an input device includes an input unit having an electrostatic sensor that performs a switching operation by detecting a change of a capacitance, and it is used for an input device in which an operator performs input operation of various information, such as figures, characters, or the like, in various electronic apparatuses, such as cellular phones, personal digital assistants (PDAs), or the like.
In such an input device, input detecting units of a plurality of electrostatic sensors, that is, electrodes are disposed on an input operation unit (input operation surface) which is formed in a casing of an electronic apparatus. In addition, according to a structure of the input device, when an input operation body composed of a conductive body, for example, a fingertip of the operator or a stylus approaches or comes in contact with portions opposite to these electrodes, a capacitance of the corresponding electrode varies, an output signal according to the variation is obtained, and input operation is performed (for example, see JP-A-2004-201175).
Further, in an input operation unit of an electronic apparatus, for example, a cellular phone, an illumination unit (key backlight) is disposed on a rear surface of an operation unit having an operation key, and an instruction display, each serves as a functional key and displays figures, characters, symbols, or the like, is provided on a surface of an operation key which is made of a transmitting material. As a result, an operation portion can be recognized easily at the time of operation (for example, see JP-A-2003-308752).
In the meantime, in recent years, various devices are required to have high performance. As a result, an input device which is an example of the various devices, should also have a high performance.
In an input device which uses an electrostatic sensor as an input operation unit, instruction display, which can be recognized by an illumination unit, should be provided on an input detecting unit of the electrostatic sensor by means of a printing method using a key top. As a result, the number of component is increased, causing the size of the device to increase. Therefore, it is not possible to achieve a device having a small size, a small thickness, and a low cost which is the general trend in recent years.
Further, in the conventional input device, since patterns of the instruction display are discriminated by shielding light illuminated from the illumination unit or transmitting it, when an area of the input operation unit is small, such as in an input operation unit of a cellular phone or a personal digital assistant, the number of the instruction display is small, and discrimination of an input function, that is, visibility of the instruction display may be deteriorated.
Furthermore, in an input operation unit of a recent input device, for example, a cellular phone, a personal digital assistant, or the like, as performances are improved, various operation, such as figure input, menu selection, mode switching, or the like, and it has been required that the diversity and visibility of the instruction display should be improved. In this case, the improvement of the visibility includes not only the improvement of the easy looking but also the improvement of the visibility or good looking of the instruction display in both of an ON state and an OFF state of the illumination.